I noticed yesterday at Mass (5th Sunday after Pentecost) the following from Matthew 5:23 -

Si ergo offers munus tuum ad altare...

This struck me as odd, and it is propagated even in the Latin Vulgate that I have (Madrid, 1965) and the altar missal which I have in my home chapel (Tours/Turonibus 1932), as well as in the Lasance missal and various online resources such as iPieta.

Shouldn't it be "si ergo offeras..." or possibly "offeres"?

I'm far from being a Latin scholar, but even to my untrained eye, this just doesn't look quite right.  Even a secular Latin online textbook shows "offers" as being the second person singular conjugation of offerre, but still...

(As a kind of homely side note, in my Protestant-influenced boyhood upbringing, you were not to say the word "fool" as a noun, because, well, you know...)

Of course TV had to get people in the habit of saying all the bad words (or good words used for bad) including fool. Mr. T and Japanese anime are the main ones that use fool.

Our Lord was not singling out one word as intrinsically evil, but rather referred to contumacious insults in general.  The anecdote I related was one from a culturally fundamentalist Protestant environment (my immediate family had no particular religious affiliation and we rarely attended any sort of church), such that they saw that one particular word as one you could never, ever say with regard to a person (as opposed to using the verb "fool").  We are not talking about highly educated people here.

The Latin word is fatue, and in Greek it is μωρέ (more), from which we get the word "moron".

I realize that my alarm yesterday in seeing offers was entirely without foundation, it's simply a version of the verb offerre with which I was unfamiliar.  You can never learn enough about Latin.

I am not a Latin scholar or anything but I did notice that the next verse actually has "offeres" (a different tense).  Perhaps offerre is an irregular verb or has an exception?  I understand where your question is coming from though.  Curious to see what the experts say. 

5:23} Si ergo offers munus tuum ad altare, et ibi recordatus fueris quia frater tuus habet aliquid adversum te:
{5:23} Therefore, if you offer your gift at the altar, and there you remember that your brother has something against you,

{5:24} relinque ibi munus tuum ante altare, et vade prius reconciliari fratri tuo: et tunc veniens offeres munus tuum.
{5:24} leave your gift there, before the altar, and go first to be reconciled to your brother, and then you may approach and offer your gift.

Actually, it's interesting that you should quote both verses, as I found the following from https://vulgate.org/nt/gospel/matthew_5.htm :

23 si ergo offeres munus tuum ad altare et ibi recordatus fueris quia frater tuus habet aliquid adversum te

If therefore thou offer thy gift at the altar, and there thou remember that thy brother hath anything against thee;

24 relinque ibi munus tuum ante altare et vade prius reconciliare fratri tuo et tunc veniens offers munus tuum

Leave there thy offering before the altar, and go first to be reconciled to thy brother, and then coming thou shalt offer thy gift.

They've got it the other way around!

I looked it up, and offerre is indeed an irregular verb.  Here's the present indicative conjugation: